Thermionic cathode



Aug. 10, 1954 (3. ROGERS E TAL THERMIONIC CATHODE Filed Jan. 25, 1952 7111111111111!!!III/IIIIIIl/In;

/ n IIIIIIIIIIII/IIIIIIIIIIA Inventor D.C. ROG E R5 ww. MARSH Attorney Patented Aug. 10, 1954 THERMIONIC CATHODE Douglas Cecil Rogers and Walter Warwick Marsh, London, England, assignors to International Standard Electric Corporation, New York, N. Y.

Application January 25, 1952, Serial No. 268,264

Claims priority, application Great Britain February 8, 1951 2 Claims.

The present invention relates to electrode as semblies for electron discharge devices and is particularly concerned with the construction and assembly of a pair of indirectly heated cathodes adapted to share a common heater.

In many types of dual thermionic valves containing two electrode structures within the same envelope it is convenient to arrange these backto-back, particularly when the structures comprise a common electrode such as an anode or grid. Thus a double triode valve maybe arranged with anodes opposite respective emitting surfaces coated on either side of a common rectangular cathode sleeve. On the other hand it is frequently desired that the cathodes should be electrically separate; where the circuit arrangements permit, it is desirable in such cases that there should be but one heater, as, unless the anodes are arranged to surround their respective cathodes, a large amount of the cathode heating power may be wasted.

According to the present invention there is provided an electrode assembly for an electron discharge device having at least an anode and a pair of separate cathodes, the two cathodes being arranged substantially to enclose between them a common cathode heater.

The invention will be described with reference to the accompanying drawing in which:

Fig. 1 shows in perspective an arrangement of a pair of cathodes according to the present invention, and

Fig. 2 shows a section through the assembly of a double triocle valve according to the invention.

In the drawing two cathode members I and 2 are shown located apart by insulating plates 3 and I. The members I and 2 are coated with electron emissive material on the sides facing away from one another and opposite their respective anodes. In Fig. 2 separate anodes 5 and 6 are shown, although it is to be understood that the cathode arrangement of the invention may also be adopted for assemblies having a common anode. Opposite edges of the cathode members are turned over through a reflex angle as indicated at 1 and 8. The central apertures in the plates 3 and i are shaped so that the turned-over edges are gripped by the walls of the aperture. The material of the oathode members I and 2 should be sufiiciently resilient for the turned-over edges to exert pressure upon the walls of the apertures in plates 3 and 4 to maintain the cathode members in position.

In the embodiment shown in the drawing, the apertures in the plates 3 and 4 are formed with lugs 9 and It at either end forming an acute angle with the long sides of the aperture, so that the edge portions of the metal members I and 2 seat firmly therein.

As is shown in Fig, 2, a common heater II is substantially enclosed by the pair of cathodes, the turned-over edges of which are arranged to project somewhat into the enclosure so as to shield, in large measure, the end walls of the plates 3 and 4 from direct radiation by the heater.

We have found with a construction similar to that shown in the drawing that there is but little heat loss from the gap between the two cathode members; the heating efiiciency is nearly as good as with a single cathode coated on both sides and represents a considerable improvement over an assembly having two separate cathode sleeves each enclosing its own heater but being coated on only one side with emissive material.

In the embodiment shown in Fig. 2 a common grid I2 surrounds both cathodes, the grid being formed as a wire winding between two supports I3 and I4 mounted between the plates 3 and 4. The anodes 5 and 6 are similarly mounted between these plates, the dual assembly being adapted for use as a grounded grid valve in a push-pull circuit and is similar, but for the cathode and grid construction, to that disclosed in our co-pending application Serial No. 268,263, filed January 25, 1952.

While the principles of the invention have been described above in connection with the specific embodiments and particular modifications thereof, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of the invention.

What we claim is:

1. An electrode assembly comprising an electron discharge device having at least one anode and two separate electron emissive cathodes, comprising a pair of resilient metal elements each having opposite edges turned inwardly at a reflex angle, said elements forming said separate cathodes, a plate of insulating material supporting said cathodes, said supporting plate having an aperture fitting said members and having protruding lugs extending into the aperture to provide supporting pressure for the turned edges of said resilient member, whereby a substantially enclosed volume is provided between said cathodes, and means providing a. common heater for said separate cathodes within said substantial enclosed volume.

2. An electron assembly according to claim 1, wherein-peach? of said 'resilient elements" is. substantially rectangular, whereby said turned-in edges shield said insulating member from direct 4 heat from said heater, except through a narrow slot.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,671,598 Mavrogenis May 29, 1928 1,727,373 Macksoud Sept. 10, 1929 2,031,411 Fury Feb. 18, 1936 2,444,242 Blewett June 29, 1948 2,527,166 Walsh Oct. 24, 1950 

